XDG_RUNTIME_DIR on a system with no "logins"

[Jan Engelhardt]

On Tuesday 2019-12-17 18:55, Guillermo Rodriguez wrote:

>Hi all,
>
>Weston requires XDG_RUNTIME_DIR to exist. The specification for this
>(https://specifications.freedesktop.org/basedir-spec/latest/ar01s03.html)
>says:
>
>===
>$XDG_RUNTIME_DIR defines the base directory relative to which
>user-specific non-essential runtime files and other file objects (such
>as sockets, named pipes, ...) should be stored. The directory MUST be
>owned by the user, and he MUST be the only one having read and write
>access to it. Its Unix access mode MUST be 0700.
>
>The lifetime of the directory MUST be bound to the user being logged
>in. It MUST be created when the user first logs in and if the user
>fully logs out the directory MUST be removed. If the user logs in more
>than once he should get pointed to the same directory, and it is
>mandatory that the directory continues to exist from his first login
>to his last logout on the system, and not removed in between. Files in
>the directory MUST not survive reboot or a full logout/login cycle.
>===
>
>But how is this done for a system where normally no users "log in",
>e.g. a fixed-function embedded system with a graphical user interface?

Well you simply create the directory before running the program that desires
said directory. Does not matter if the user identity change is by way of
a system manager, runuser(8), or login(8)/PAM (as called by xdm/etc.).


kiosk.service
 User=npc
 ExecStart=/home/npc/startx.sh

startx.sh:
 export XDG_RUNTIME_DIR=/home/npc/xdg
 rm -Rf "$XDG_RUNTIME_DIR"
 mkdir "$XDG_RUNTIME_DIR"
 weston # or whatever